1. Field of the Invention
The present invention relates to a method of producing a semiconductor optical device.
2. Description of the Related Art
A ridge type semiconductor optical device is known as a conventional art, which is described in Non-Patent Reference (IEEE PHOTONICS TECHNOLOGY LETTER, VOL. 18, NO. 12, JUN. 15, 2006). FIGS. 7A to 7D show an example of a method of producing a conventional ridge type semiconductor optical device. As shown in FIG. 7A, first, a stacked semiconductor layer 104 including an active layer 102, a cladding layer 103, etc. is formed on a semiconductor substrate 101. A mask pattern 105, for example, composed of silicon nitride (SiN) is formed on the stacked semiconductor layer 104. Next, as shown in FIG. 7B, a ridge 106 is formed by a dry etching process using the mask pattern 105. Next, as shown in FIG. 7C, after the mask pattern 105 is removed, a SiO2 film 107 is formed thickly so as to cover the ridge 106. Next, as shown in FIG. 7D, by polishing the surface of the SiO2 film 107, the SiO2 film covering the ridge 106 is removed. As a result, the ridge 106 is exposed, and the top surface of optical device including the ridge structure is planarized.